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Chapter 9 Key Terms

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A horizon
The top layer of soil that has most nutrients and humus, most fully evolved layer dark in color and has minerals grains, decaying leaves, roots, insects, and worms.
B Horizon
The layer of soil that is often called subsoil that usually consists of clay and other particles.
Bedrock
The continuous mass of solid rock that makes up Earth's crust.
C Horizon
Beneath B horizon, contains weathered parent material.
Clay
The smallest type of soil particles that have the capacity to absorb and hold water.
Contour farming
Plowing furrows sideways across a hillside to help prevent formation of rills and guillies.
Crop rotation
Process of changing what is planted in a field from year to year in order to restore soil nutrients.
Desertification
The process by which formerly fertile lands become increasingly arid, unproductive, and desert-like.
Dust Bowl
Term used to describe the central and southern Great Plains in the 1930s when the region sustained a period of drought and dust storms.
E Horizon
Very little humus. Minerals leached from rainwater and minerals already in the soil that resist leaching. Below A above B.
Intercropping
Strip cropping, planting bands of different crops across a hillside.
Leaching
The removal of soluble substances from rock, ore, or layers of soil due to the passing of water.
Loam
A type of topsoil that is rich in minerals and has lots of humus.
Monoculture
The agricultural practice of producing or growing one single crop over a wide area.
Natural Resources
Materials found in nature that are used by living things.
Conservation Service
A group that helps the conservation of resources and farmland.
No Till Agriculture
The process of not plowing land and using herbicides to prevent some types of weeds from surfacing.
O Horizon
The uppermost horizon of soil, primarily made up of organic material and humus.
Parent material
Inorganic material base from which soil is formed.
R Horizon
The bedrock that lies below all of the other layers of soil.
Salinization
When small traces of salt in freshwater irrigation builds up in arid climates, rendering the land worthless.
Sand
Small particles of various minerals and broken rocks, the result of weathering and erosion.
Shelterbelt
Row of trees that protects farm from wind.
Silt
A mixture of tiny bits of soil and rock carried and deposited by a river.
Soil profile
The sequence of soil horizons from the surface down to the underlying bedrock.
Terracing
Stepped ridges carved into hillsides help retain water and reduce erosion.
Weathering
The breaking down of rocks and other materials on the Earth's surface.